It is on the left panel. Any item in the left panel (folder) is called a "key"

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You can also go to it by "find" command:

Right click on "HKEY_LOCAL_MACHINE"
and
then "find" and in the dialogue box, write "OEMbackground"
just as shown above (only click on "value" )

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Double click on "Background" , you will see
the "OEMBackground" on the right panel. Any item on the right
panel is called "value".

Double click on "OEMBackground" value. When
you see the box, change the value data from 0 to 1.

If the "OEMBackground" value doesn't exit, just
right click on the right panel of "Background" key and then click
new>32bit DWORD value. Then rename the new value to
"OEMBackground" and double click that. Then in the value data, write
1.

Now click ok and close the registry editor.

2. Creating folders

Go to "C:\Windows\System32\Oobe" folder. Now create a new folder here named "info". If asked for user account control, click "continue".

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In the same way, create a folder named "backgrounds" inside the "info" folder.

3. Preparing the wallpaper

As you are changing the screen, you can obviously use any image as your wallpaper. Here is only two condition, "The resolution of the image must be same as your display resolution & must be smaller than 256KB". You can see your "Control Panel\Appearance and Personalization\Display\Screen Resolution"

Now resize/edit your desired image and change the resolution to your display resolution and rename the image as "backgroundDefault.jpg". Note that the image type must be jpg.

Now copy or move the file to "Windows\System32\Oobe\info\backgrounds" folder. Click continue if user account control prompts.

ALL DONE !!!!

Now, click "Ctrl+Altr+Delete" together and see the difference !!!

If you want to alter the shadows:

To show shadows behind the Log on screen to give the text and images a 3D-like look, launch the registry editor again and go to:

Double click on the "LogonUI" key and on the right panel right click and create a new value by clicking new>32bit DWORD value. Rename it to "ButtonSet". Double click this value and enter value data as bellow:

0 for Light shadow

1 for Dark shadow

2 for No shadow

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The "ButtonSet" value allows you to adjust or disable the text and button shadows.

***Very important:

(For some safety reasons in case you are not familiar with this registry editor)

Before the step 4 >>

Just right click on the folder/item/key “uninstall” and then click on export then in your desktop, save this file with any name just as uninstall.reg.

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It’s called the “backup of registry keys”.

If there are some problems you find after doing all the steps, you can just roll back to your previous state using this backed up registry file.

To do it>> just double click the registry file and click ‘yes’. Nothing else.